Before the deployment of any vehicular communication system, security and privacy issues have to be resolved. In this paper, for achieving secure and privacy preserving communications, an easily implementable PKI-based protocol is proposed. Security requirements for vehicular communications are defined and a detailed definition of the scheme, which uses shared asymmetric keys and PKI techniques to provide anonymous and secure communications, is given. Furthermore, the proposed protocol is evaluated against the defined security requirements. Providing privacy and security, the proposed scheme does not introduce any complexity and computational overheads.